I can no longer recommend the tailgate struts that I purchased and used as outlined in this post. Please refer to the updated post for the newer and stronger aftermarket struts I purchased and used for my car:
Original Post 4-15-17:
My tailgate struts have been going dead on my 2003 Toyota 4Runner, so just like I did on my hood struts, I ended up replacing my tailgate struts as well.
The part is a direct replacement. You simply need to remove the existing bolts on each end of the tailgate strut (meanwhile using something the help prop up the tailgate) and the strut comes off. Then install the new struts and tighten in the bolts, and it is as simple as that.
With parts such as this, 3rd party products work really well and are so much cheaper than their OEM counterparts. I looked on eBay noticed there are quite a few options, but I had an excellent experience with this seller. The item I purchased for about $26 for a set can be found on eBay here.